Cooling system with two heat exchangers and vehicle with a cooling system

ABSTRACT

A cooling system with icing protection for a coolant flowing therein comprises a first heat exchanger to withdraw coolant thermal energy. The first heat exchanger uses a first fluid flow as a heat sink. A second heat exchanger withdraws thermal energy from the coolant using a second fluid flow, differing from the first fluid flow, as a heat sink. A conveyor device supplies the coolant to the first and second heat exchangers. The cooling system comprises a valve to regulate a volumetric flow of the coolant supplied to the second heat exchanger, a temperature sensor configured to measure a temperature of the coolant downstream of the first and/or second heat exchanger, and a control unit to control a delivery rate of the conveyor device and/or the volumetric flow such that the temperature measured by the temperature sensor does not fall below a predetermined coolant viscosity.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of the German patent application No. 10 2018 114 353.2 filed on Jun. 15, 2018, the entire disclosures of which are incorporated herein by way of reference.

FIELD OF THE INVENTION

The invention relates to a cooling system with two heat exchangers and to a vehicle with such a cooling system. In particular, the invention relates to a cooling system with a control device which makes it possible to supply a volumetric flow of a coolant in the cooling system to the second heat exchanger in such a manner that the coolant downstream of the first and/or second heat exchanger does not fall below a temperature which corresponds to a predetermined viscosity of the coolant.

BACKGROUND OF THE INVENTION

In vehicles, such as, for example, aircraft, buses, trains, ships, etc., many heat sources are installed, with passengers or freight also being able to generate and/or output heat. For the cooling of the heat sources, use is generally made of a cooling system which comprises a coolant which absorbs heat from the heat sources and outputs same to a heat sink. Ambient air which is thermally coupled to the coolant by means of heat exchangers is generally used as the heat sink.

The cooling system firstly has to be configured to be able to output the maximum waste heat from the heat source(s) to the heat sink depending on the temperature of the ambient air and waste heat generated by the heat source(s), and secondly has to be configured to prevent the coolant from being too severely cooled. For example, with little waste heat and/or at very low temperatures of ambient air, the viscosity of the coolant may greatly increase after cooling in the heat exchanger. However, this impairs the possibility of conveying the coolant by means of a conveyor device or may even damage the conveyor device.

Conventional cooling systems, therefore, provide a bypass line through which heated coolant can be conducted past the heat exchanger and can be mixed there with the cooled coolant. As a result, the viscosity of the coolant upstream of the conveyor device can be improved. Alternatively, a shut-off apparatus, for example a flap, can also be provided which limits an air flow of the ambient air to the heat exchanger such that the cooling power of the heat exchanger is reduced.

SUMMARY OF THE INVENTION

The invention is based on an object of providing an improved cooling system which is capable of using simple means to avoid overcooling of the coolant. Furthermore, the invention is based on an object of providing a vehicle with such a cooling system.

According to a first aspect, a cooling system with icing protection for a coolant flowing in the cooling system comprises a first heat exchanger which is configured to withdraw thermal energy from the coolant, wherein the first heat exchanger uses a first fluid flow as a heat sink, and a second heat exchanger which is configured to withdraw thermal energy from the coolant, wherein the second heat exchanger uses a second fluid flow, which differs from the first fluid flow, as a heat sink. The first and second fluid flow can involve the same fluid or a different fluid. For example, both the first heat exchanger and the second heat exchanger can use air as a heat sink, wherein the air flows flow parallel to one another. In other words, the first and second heat exchangers are arranged parallel to each other with regard to the fluid flow/flows used as a heat sink.

In another configuration, one of the two fluid flows can be an air flow while the other is formed from water or from another liquid, or the two fluid flows comprises a liquid.

The cooling system can furthermore comprise a conveyor device, which is configured to supply the coolant to the first heat exchanger and to the second heat exchanger. For example, the conveyor device can be provided in the form of a pump for conveying a liquid or gaseous coolant. Of course, the conveyor device can also be provided in the form of a compressor which supplies gaseous coolant to the first and second heat exchangers.

Furthermore, the cooling system comprises a valve which is configured to regulate a volumetric flow of the coolant which is supplied to the second heat exchanger. For example, the valve can (infinitely variably) change a cross section of a valve portion, through which the coolant flows, in such a manner that the valve completely closes or completely opens the cross section or, in an intermediate position, leaves part of the cross section open for the throughflow with coolant.

The cooling system furthermore contains at least one temperature sensor which is configured to measure a temperature of the coolant downstream of the first heat exchanger and/or of the second heat exchanger, and a control unit which is configured to control a delivery rate of the conveyor device and/or the volumetric flow regulated by the valve in such a manner that the temperature measured by the temperature sensor does not fall below a threshold value which corresponds to a predetermined viscosity of the coolant. In other words, the conveyor device and the valve are regulated by the control unit in such a manner that the coolant downstream of the two heat exchangers always has a certain temperature, and therefore the viscosity of the coolant has an upwards limit. As the temperature rises, the viscosity of the coolant decreases, and therefore the coolant downstream of the two heat exchangers and therefore upstream of the conveyor device is likewise present with the viscosity having an upwards limit.

Use can be made, for example, of a water-based coolant. This includes ethylene glycol water (EGW) in a mixture ratio of, for example, 50/50, or propylene glycol water (PGW) in a mixture ratio of 60/40. These coolants are distinguished by good heat transport capacity with a conveying capability at low temperatures, and also by high burst protection, i.e., the coolant does not expand further even at lower temperatures and with possible freezing, and therefore the coolant-containing devices are not damaged. The temperature level at which the mixtures may lose their normal fluid property and, in particular, can no longer be expediently conveyed by centrifugal pumps is at approx. −32° C. to −34° C. for EGW and approx. −43° C. to −45° C. for PGW, at the mixture ratios specified.

Other heat carriers, such as silicone oils or certain fluorinated hydrocarbons (tradenames Novec, Galden) are generally capable of being conveyed even at lower temperatures although the viscosity also greatly increases there. However, these are significantly inferior in specific heat transport capability to the water-based heat carriers and are also more expensive.

In conventional cooling systems, the arrangement of a bypass line conducting the coolant past the generally single heat exchanger can lead to the coolant being virtually completely guided through the bypass line when little cooling is required and/or at very low temperatures of the heat sink. Coolant remaining in the heat exchanger, however, may be overcooled here, i.e., the coolant is cooled to such an extent that the viscosity of the coolant increases such that the coolant can no longer be conveyed in the cooling system, or leads to such high pressure losses in the heat exchanger that the flow rate is greatly impaired. For example, the coolant can freeze in the heat exchanger or can crystalize or freeze on the walls of the coolant-guiding lines in the heat exchanger such that the cross section of the heat exchanger is greatly restricted or is entirely closed. In this case (and, in particular, at very low temperatures of the fluid forming the heat sink), the cooling system can fail since no more cooling at all takes place when a certain viscosity value is exceeded and when icing occurs. As a consequence, the heat source will overheat. De-icing (thawing) of the heat exchanger can be impossible because of the bypass line since, although closing of the bypass line increases the pressure of the coolant in the inlet region of the heat exchanger, the latter is not necessarily de-iced if no throughflow of coolant is possible.

In conventional cooling systems with a shut-off apparatus (for example a flap) for the fluid which is supplied to the heat exchanger and forms a heat sink, thawing of the heat exchanger when icing of the heat exchanger has occurred is likewise not easily possible. Even if the shut-off apparatus entirely stops the fluid flow, the cross section which is already closed within the heat exchanger for the coolant can be thawed (opened) only slowly. In this time, the conveyor device of the cooling system can incur damage and/or the cooling power provided for the heat source is insufficient. In addition, the shut-off apparatus constitutes a resistance in the fluid flow serving as a heat sink, the resistance leading to a reduction in the energy efficiency of the overall system (for example of a vehicle). If the fluid flow is generated, for example, by the movement of the vehicle, for example ambient air which is guided through a ram air duct, when the shut-off apparatus is closed the flow at the input of the ram air duct changes, as a result of which unfavorable flows may arise and therefore the aerodynamics of the vehicle may be impaired.

By contrast, the cooling system described here affords the advantage that the control unit prevents overcooling of the coolant. Overcooling is understood here as meaning the exceeding of a threshold value of the viscosity of the coolant, and also freezing or crystallizing of at least part of the coolant within or downstream of the heat exchanger. By controlling the delivery rate of the conveyor device and/or of the volumetric flow of the coolant being supplied to the second heat exchanger through the valve, a predetermined quantity of coolant can always be guided through the first heat exchanger while, when a higher cooling power is required, coolant can also be guided through the second heat exchanger and cooled. The first heat exchanger can therefore be dimensioned in such a manner that overcooling of the coolant only by the first heat exchanger is not possible. For example, the first heat exchanger can be of smaller dimensions than in conventional cooling systems, and therefore, when the fluid serving as a heat sink is at customary temperatures which can be anticipated and in the event of customary cooling powers which can be anticipated, the heat exchanger cannot cool the coolant in such a manner that the viscosity exceeds the threshold value. An increased cooling power of the cooling system is made possible by opening the valve and/or increasing the delivery rate through the conveyor device.

In a variant configuration, the cooling system can furthermore comprise a first coolant line which is configured to conduct coolant heated by a heat source to the first heat exchanger, and a second coolant line which branches off from the first coolant line and is configured to at least partially conduct the coolant heated by the heat source to the second heat exchanger. The valve is arranged in the second coolant line, in this case, and is configured to regulate the volumetric flow of the coolant flowing through the second coolant line. This arrangement permits the use of a single valve (a valve with only an input and an output) which is arranged within the second coolant line and regulates the flow through the second coolant line.

Conventional cooling systems with a bypass line generally have a three-way valve which regulates the respective volumetric flow into the bypass line and to the heat exchanger. However, these three-way valves are more expensive, more maintenance-intensive and heavier. By contrast, in the cooling system described here, the volumetric flow to the second heat exchanger is prevented by closing the single valve in the second coolant line, and therefore all of the coolant moved by the conveyor device is supplied to the first heat exchanger.

In another variant configuration, the cooling system can furthermore comprise a first coolant line which is configured to conduct coolant heated by a heat source to the first heat exchanger, a third coolant line which is configured to conduct coolant cooled by the first heat exchanger to the second heat exchanger, and a fourth coolant line, which branches off from the third coolant line and is configured to guide coolant past the second heat exchanger. Here, the valve is arranged in the fourth coolant line and is configured to regulate the volumetric flow of the coolant flowing through the fourth coolant line such that the volumetric flow of the coolant supplied to the second heat exchanger is regulated. Also here, a simple and cost-effective valve which merely regulates the flow through the fourth coolant line can be used. By closing of the valve, the flow through the fourth coolant line is stopped, and therefore the coolant leaving the first heat exchanger flows completely into the second heat exchanger. By (partial) opening of the valve, at least some of the coolant leaving the first heat exchanger is guided past the second heat exchanger through the fourth coolant line. Since the second heat exchanger provides a higher flow resistance for the coolant than the fourth coolant line with the valve, when the valve is open the coolant will predominantly (if not completely) flow through the fourth coolant line.

In a further variant configuration, the at least one temperature sensor can comprise at least one of the following sensors:

-   -   a (first) temperature sensor which is configured to measure a         temperature of the coolant directly upstream of the conveyor         device;     -   a (second) temperature sensor which is configured to measure a         temperature of the coolant directly downstream of the first heat         exchanger;     -   a (third) temperature sensor which is configured to measure a         temperature of the coolant directly downstream of the second         heat exchanger;     -   a (fourth) temperature sensor, which is configured to measure a         temperature of the coolant directly upstream of the heat source;     -   a (fifth) temperature sensor which is configured to measure a         temperature of the coolant directly downstream of the heat         source;     -   a (sixth) temperature sensor which is configured to measure a         temperature of the first fluid flow directly upstream of the         first heat exchanger; and     -   a (seventh) temperature sensor which is configured to measure a         temperature of the second fluid flow directly upstream of the         second heat exchanger.

“Directly upstream” or “directly downstream” here means an arrangement of the sensor in the direct vicinity of the respective cooling system component. That is to say, a short section of a coolant line or fluid line can be located between sensor and component, or the sensor is arranged in the region of a connection of the coolant line or fluid line to the component. The purpose of this arrangement is to measure the temperature of the coolant or fluid at the point where a significant temperature change no longer takes place because of a further conduction by line as far as the component.

Alternatively or additionally, each sensor can be replaced or supplemented by a pressure sensor.

The control unit here can be configured to receive corresponding signals from each of the temperature and/or pressure sensors, the signals representing the temperature/pressure of the coolant prevailing at the respective temperature and/or pressure sensor. For example, the control unit can receive analogue and/or digital signals from at least one of the sensors in order to determine the temperature/pressure of the coolant and/or fluid flow. Furthermore, from the signals of the sixth and seventh temperature sensor measuring the temperature of a fluid flow, the control unit can draw at least conclusions regarding a possible temperature of the coolant after the latter has passed through the associated heat exchanger. For example, from the customarily known power parameters of the associated heat exchanger and the received sensor signal, the control unit can determine the lowest possible temperature of the coolant after the latter has passed through the associated heat exchanger.

In a further variant configuration, the cooling system can furthermore comprise a fluid flow line which is configured to branch off at least part of the first fluid flow downstream of the first heat exchanger and to supply same to the second fluid flow upstream of the second heat exchanger. Alternatively or additionally, the cooling system can also comprise a fluid flow line which is configured to branch off at least some of the second fluid flow downstream of the second heat exchanger and to supply same to the first fluid flow upstream of the first heat exchanger. The cooling system can optionally also comprise at least one control apparatus which is configured to regulate a volumetric flow of the fluid flow branched off, or of the two fluid flows branched off, through the respective fluid flow line. In this variant configuration, it is possible to provide a fluid flow having an increased temperature to one of the two heat exchangers. For example, a heat exchanger which is still frozen can thereby thaw because of the heated fluid flow after the latter has passed through the other heat exchanger. The control device can be configured to regulate the control apparatus for controlling the volumetric flow of the branched-off fluid flow in order to heat the other fluid flow.

In a further refinement, the first and/or second heat exchanger is designed in such a manner that the coolant enters on a side of the respective heat exchanger on which the fluid flow exits, and exits on a side of the respective heat exchanger on which the fluid flow enters. The opposed passage by the coolant flow and the fluid flow through the heat exchanger increases the efficiency of the cooling system. The required fluid flow can thereby be reduced, which also permits a reduction in the necessary cross section for the fluid flow and the associated reduction in vortexes on a skin of the vehicle.

In yet another refinement, the first heat exchanger and/or the second heat exchanger can be a matrix heat exchanger, a skin heat exchanger or a combination of a matrix heat exchanger and a skin heat exchanger. A matrix heat exchanger permits a more compact design since a larger surface between coolant flow and fluid flow is made possible. By contrast, the skin heat exchanger does not require any fluid inlet and fluid outlet in a skin of the vehicle, as a result of which vortexes are reduced in comparison to a matrix heat exchanger.

According to a further aspect, a vehicle comprises a cooling system according to the first aspect or one of the associated variant refinements.

Furthermore, the vehicle can comprise a heat source which is cooled by the cooling system. The heat source can be, for example, a passenger cabin, a freight hold, a cockpit, an avionics component, a hydraulic component and/or an electronic component.

The refinements, variants and aspects described here can furthermore be combined as desired, and therefore further variant refinements which are not explicitly described are included in the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will be described in more detail below with reference to the drawings.

FIG. 1 schematically shows a conventional cooling system with a bypass line,

FIG. 2 schematically shows a conventional cooling system with a shut-off apparatus in a cooling air line,

FIG. 3 schematically shows a cooling system according to the present disclosure,

FIG. 4 schematically shows a variant of the cooling system according to the present disclosure,

FIG. 5 schematically shows a fluid flow control for a cooling system, and

FIG. 6 schematically shows a vehicle with a cooling system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention describes a cooling system with a control device which makes it possible to supply a volumetric flow of a coolant in the cooling system to a second heat exchanger in such a manner that the coolant downstream of a first and/or the second heat exchanger does not exceed a predetermined viscosity, and also a vehicle with such a cooling system.

FIG. 1 schematically shows a conventional cooling system 300 with a heat exchanger 301 and a heat source 302. The heat exchanger 301 is thermally coupled to a heat sink, for example an air flow 303, in order to output thermal energy generated by the heat source 302. In the cooling system 300, coolant is moved in the flow direction, illustrated by an arrow, by a conveyor device 304, and therefore the coolant after absorbing thermal energy from the heat source 302 is supplied by a coolant line 305 to the heat exchanger 301. In the event that the air flow 303 too greatly cools the coolant in the heat exchanger 301, a bypass line 306 is provided which conducts the coolant past the heat exchanger 301 and, upstream of the conveyor device 304, brings the coolant together with the cooled coolant from the heat exchanger 301. As a result, the coolant flowing to the conveyor device 304 has a higher temperature, and therefore, for example, a viscosity of the coolant can be limited. The rate of the coolant flowing through the bypass line 306 is controlled by a three-way valve 307. The valve 307 permits complete or partial deflection of the coolant from the line 305 into the bypass line 306 and/or the heat exchanger 301.

FIG. 2 schematically shows another conventional cooling system 310 that generally corresponds to the cooling system 300 from FIG. 1. Instead of a bypass line 306 and associated three-way valve 307 (FIG. 1), the coolant line 305 leads directly into the heat exchanger 301. In order to prevent the coolant which leaves the heat exchanger 301 from being too greatly cooled and therefore having too high a viscosity, a cooling air line 311 through which the air flow 303 flows and is supplied to the heat exchanger 301 can be equipped with a shut-off apparatus 312. The shut-off apparatus 312, for example a flap, can limit the air flow 303 or even stop same entirely, i.e., can completely close the cooling air line 311. As a result, the amount of heat which can be absorbed by the air flow 303 acting as a heat sink is limited, and therefore the coolant after leaving the heat exchanger 301 does not fall below a desired temperature.

FIG. 3 schematically shows an improved cooling system 10 which can transport away waste heat generated by a heat source 20. For this purpose, the cooling system 10 has a first heat exchanger 101. The latter can withdraw thermal energy from a coolant flowing through the cooling system, wherein the heat exchanger 101 uses a first fluid flow 201 as a heat sink. The fluid flow 201 can be an air flow or else a liquid which is capable of absorbing thermal energy and optionally of transporting same away. The fluid flow 201 can thus be an air flow into a ram air duct, the air flow being guided past or through the heat exchanger 101 by means of the movement of a vehicle, or stationary air in a region of the vehicle that outputs heat to the environment via the skin of the vehicle, such as, for example, a stowage space. The liquid used can be a coolant from a different cooling circuit or a stationary fluid, such as, for example, a fresh water tank or a fuel tank.

A conveyor device 105 drives the coolant such that the latter can continuously absorb thermal energy from the heat source 20 and can continuously output thermal energy to the fluid flow 201. The lines necessary for this purpose are illustrated in FIG. 3, but are not all explained in detail since they are conventional coolant lines of a cooling system. The coolant lines form a circuit, as is shown in FIG. 3.

In order to prevent overcooling of the coolant in the heat exchanger 101, i.e., in order to prevent the cooling of the coolant below a temperature in which the coolant has too high a viscosity, a second heat exchanger 102 is provided in the cooling system 10. The second heat exchanger 102 is configured to withdraw thermal energy from the coolant and, for this purpose, uses a second fluid flow 202 as a heat sink. The second fluid flow 202 differs from the first fluid flow 201. The first heat exchanger 101 can therefore be of smaller dimensions than in conventional systems since the second heat exchanger 102 can be “switched to” if a greater cooling power is required. It can thereby be ensured that coolant leaving the first and second heat exchanger 102 is not overcooled. For example, the first fluid flow 201 can be an air flow (for example in a ram air duct) while the second fluid flow 202 is a liquid which acts as a heat sink. The liquid here does not have to form any moving fluid flow as such, but rather can be a liquid reservoir, such as, for example, a fresh water tank.

Of course, the first and second fluid flow 201, 202 can also have the same origin. For example, the first and second fluid flow 201, 202 can each be part of an air flow in a ram air duct, wherein the ram air duct has only one inlet and one outlet.

In each case, the two heat exchangers 101, 102 are arranged parallel to each other with respect to the fluid flows 201, 202 in the cooling system 10 illustrated in FIG. 3.

In addition, the cooling system 10 illustrated in FIG. 3 also has a parallel arrangement of the heat exchangers 101, 102 with respect to the coolant flow. In other words, the conveyor device 105 supplies the coolant both to the first heat exchanger 101 and to the second heat exchanger 102, wherein a valve 111 can regulate a volumetric flow of the coolant which is supplied to the second heat exchanger 102. In other words, the valve 111 regulates the volumetric flow of the coolant which is cooled by the second heat exchanger 102.

The valve 111 could indeed be designed as a three-way valve, and therefore the valve 111 conducts a coolant flowing through a coolant line 141 coming from the heat source 20 either to the first heat exchanger 101 or to the second heat exchanger 102 or to the two heat exchangers 101, 102. However, in the variant illustrated in FIG. 3, a more cost-effective “normal” valve is arranged in a coolant line 142 which branches off from the coolant line 141 coming from the heat source 20 and leads to the second heat exchanger 102. By closing of the valve 111, the coolant is guided exclusively through the first heat exchanger 101 and the second heat exchanger 102 is “disconnected.”

A control unit 130 is provided in the cooling system 10 in order to control the conveyor device 105 and/or the valve 111. The control unit 130 can thus send a signal to the conveyor device 105 in order to determine a delivery rate of the conveyor device 105, i.e. a volumetric flow of the coolant moved by the conveyor device 105 in the cooling system 10. The valve 111 can be regulated by the control unit 130 to the effect that a throughflow cross section of the valve 111 is set, after which a volumetric flow of the coolant through the second heat exchanger 102 is regulated. The control unit 130 is configured to control the delivery rate of the conveyor device 105 and/or the volumetric flow regulated by the valve 111 in such a manner that a temperature of the coolant does not fall below a threshold value which corresponds to a predetermined viscosity of the coolant. It is thereby prevented that the coolant can be moved only very poorly, if at all, by the conveyor device 105, and therefore the conveyor device 105 is saved from damage.

The control unit 130 here can be configured in such a manner that the coolant temperature downstream of the first heat exchanger 101 and/or of the second heat exchanger 102 or (directly) upstream of the conveyor device 105 does not fall below the threshold value. For this purpose, at least one temperature sensor 121 can be arranged in the cooling system 10 and measures a temperature of the coolant.

Alternatively or additionally, the control unit 130 can be configured in such a manner that a coolant pressure downstream of the first heat exchanger 101 and/or of the second heat exchanger 102 or (directly) upstream of the conveyor device 105 does not fall below a threshold value. For this purpose, at least one pressure sensor (not illustrated separately) can be arranged in the cooling system 10 and measures a pressure of the coolant. The system properties described below for temperature sensors apply equally to pressure sensors.

The temperature sensor 121 can be arranged upstream of the conveyor device 105. Of course, the one temperature sensor or an additional temperature sensor 122 can be arranged (shortly or directly) downstream of the first heat exchanger 101 and/or a temperature sensor 123 can be arranged (shortly or directly) downstream of the second heat exchanger 102 in the cooling system 10. Further temperature sensors 124 and 125 can be arranged (shortly or directly) upstream of the heat source 20 and/or (shortly or directly) downstream of the heat source 20 in the cooling system 10.

Of course, the temperature of at least one of the fluid flows 201, 202 can also be measured. For this purpose, temperature sensors 126 and 127 can be provided in the cooling system 10, the temperature sensors respectively measuring a temperature of the first fluid flow 201 (shortly or directly) upstream of the first heat exchanger 101 and a temperature of the second fluid flow 202 (shortly or directly) upstream of the second heat exchanger 102.

The control unit 130 can be connected to each of the sensors in order to draw conclusions regarding the viscosity of the coolant on the basis of the temperature and/or the pressure. On the basis of the determined temperature and/or pressure, the control unit 130 can determine and regulate the delivery rate of the conveyor device 105 and/or the volumetric flow of the coolant which flows from the valve 111 to the second heat exchanger 102. The control unit 130 can thereby prevent the viscosity of the coolant from exceeding a critical value in which the cooling system no longer functions correctly.

FIG. 4 schematically shows a variant of the cooling system 10 according to the present disclosure, wherein the coolant line 142 does not branch off from the coolant line 141. On the contrary, the cooling system 10 comprises a third coolant line 143 in order to conduct coolant cooled by the first heat exchanger 101 to the second heat exchanger 102. The first and second heat exchanger 101, 102 are accordingly connected in series with respect to the coolant flow. In order to control the coolant flow into the second heat exchanger, a fourth coolant line 144 is provided in the cooling system 10, the coolant line branching off from the third coolant line 143 and guiding coolant past the second heat exchanger 102. In this refinement, the valve 111 is arranged in the fourth coolant line 144 in order to regulate the volumetric flow of the coolant flowing through the fourth coolant line 144. This likewise permits regulation of the volumetric flow of the coolant through the second heat exchanger 102 by means of the control unit 130.

FIG. 5 schematically shows a fluid flow control system for a cooling system 10, wherein only the first and second heat exchanger 101, 102 of the cooling system 10 are illustrated. The other elements of the cooling system 10 can correspond to those of the variants illustrated in FIGS. 3 and 4.

The fluid flow control system can provide a fluid line 203 through which at least some of the first fluid flow 201 is branched off downstream of the first heat exchanger 101 and is supplied to the second fluid flow 202 upstream of the second heat exchanger 102. For example, a fluid duct 204, in which the first heat exchanger 101 is arranged and the first fluid flow 201 flows, can have a branch downstream (with respect to the fluid flow 201) from which the fluid line 203 extends. Similarly, a fluid duct 205 in which the second heat exchanger 102 is arranged and the second fluid flow 202 flows can have a branch or opening to which the fluid line 203 extends. In other words, the fluid line 203 forms a connection of the fluid ducts 204 and 205, wherein portions of the fluid ducts 204 and 205 are connected to each other downstream or upstream of the respective heat exchanger 101, 102.

Of course, the fluid line 203 can also be provided in the reverse direction (not illustrated). In this case, a portion of the fluid duct 205 of the second fluid flow 202 would be connected downstream of the second heat exchanger 102 to a portion of the fluid duct 204 of the first fluid flow 201 upstream of the first heat exchanger 101 by the fluid line 203.

In both cases, the fluid line 203 can comprise a control apparatus 210 which regulates a volumetric flow of the fluid flow branched off through the fluid line 203. The control apparatus 210 can be a valve, a flap or another shut-off member which is capable of closing or opening a cross section of the fluid flow line 203.

By means of the branched-off fluid flow, heated fluid can be supplied to the heat exchanger 101, 102 connected downstream in each case. This makes it possible to avoid overcooling of the coolant in the cooling system 10 if the two fluid flows 201, 202 have too low a temperature, and therefore the viscosity of the coolant cannot be kept under the desired critical value. It is also possible to deice one of the heat exchangers 101, 102, for example if the second heat exchanger 102 has not been used for a prolonged period in the cooling system 10 and the coolant located in the heat exchanger 102 has reached a very high viscosity or has frozen.

The control apparatus 210 can furthermore comprise a conveyor device (not illustrated separately) in order to move the fluid heated by a heat exchanger 101, 102 through the fluid flow line 203 to the other heat exchanger 101, 102 upstream in the direction of the respective fluid flow 201, 202.

FIG. 6 schematically shows a vehicle 11 with a cooling system 10. Although the vehicle 11 is illustrated as an aircraft, it can also be a bus, a train, a ship or another vehicle. A heat source 20 which is cooled by the cooling system 10 is arranged in the vehicle 11. The heat source 20 can be a passenger cabin, a cargo hold, a cockpit, an avionics component, a hydraulic component and/or an electronic component.

The first and/or second heat exchanger 101, 102 of the cooling system 10 can be implemented as a matrix heat exchanger or as a skin heat exchanger or in the form of a combination of a matrix heat exchanger with a skin heat exchanger. The first and/or second heat exchanger 101, 102 can thus form a skin heat exchanger on a skin of the vehicle 11, as is illustrated in FIG. 6. Of course, the first and/or second heat exchanger 101, 102 can also be arranged in the interior of the vehicle 11 and can be implemented in the form of a matrix heat exchanger. In both variants, the coolant of the cooling system 10 is thermally coupled to a fluid flow 201, 202 or to a static fluid. The fluid flows 201, 202 can be ambient air which flows along a skin of the vehicle 11 and/or flows through an inlet into a fluid duct 204, 205 into the interior of the vehicle 11.

The variants, refinements and exemplary embodiments discussed above serve merely for describing the claimed teaching, but do not restrict the latter to the variants, refinements and exemplary embodiments.

While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority. 

1. A cooling system with icing protection for a coolant flowing in the cooling system, comprising: a first heat exchanger configured to withdraw thermal energy from the coolant, wherein the first heat exchanger uses a first fluid flow as a heat sink; a second heat exchanger configured to withdraw thermal energy from the coolant, wherein the second heat exchanger uses a second fluid flow, which differs from the first fluid flow, as a heat sink; a conveyor device, configured to supply the coolant to the first heat exchanger and to the second heat exchanger, a valve configured to regulate a volumetric flow of the coolant supplied to the second heat exchanger; at least one temperature sensor configured to measure a temperature of the coolant downstream of at least one of the first heat exchanger or of the second heat exchanger; and a controller configured to control at least one of a delivery rate of the conveyor device or the volumetric flow regulated by the valve in such a manner that the temperature measured by the temperature sensor does not fall below a threshold value which corresponds to a predetermined viscosity of the coolant.
 2. The cooling system according to claim 1, furthermore comprising: a first coolant line configured to conduct coolant heated by a heat source to the first heat exchanger; and a second coolant line which branches off from the first coolant line and is configured to at least partially conduct the coolant heated by the heat source to the second heat exchanger, wherein the valve is arranged in the second coolant line and is configured to regulate the volumetric flow of the coolant flowing through the second coolant line.
 3. The cooling system according to claim 1, furthermore comprising: a first coolant line configured to conduct coolant heated by a heat source to the first heat exchanger; a third coolant line configured to conduct coolant cooled by the first heat exchanger to the second heat exchanger; and a fourth coolant line, which branches off from the third coolant line and is configured to guide coolant past the second heat exchanger, wherein the valve is arranged in the fourth coolant line and is configured to regulate the volumetric flow of the coolant flowing through the fourth coolant line such that the volumetric flow of the coolant supplied to the second heat exchanger is regulated.
 4. The cooling system according to claim 2, wherein the at least one temperature sensor comprises: a temperature sensor configured to measure a temperature of the coolant directly upstream of the conveyor device; a temperature sensor configured to measure a temperature of the coolant directly downstream of the first heat exchanger; a temperature sensor configured to measure a temperature of the coolant directly downstream of the second heat exchanger; a temperature sensor configured to measure a temperature of the coolant directly upstream of the heat source; a temperature sensor configured to measure a temperature of the coolant directly downstream of the heat source; a temperature sensor configured to measure a temperature of the first fluid flow directly upstream of the first heat exchanger; and a temperature sensor configured to measure a temperature of the second fluid flow directly upstream of the second heat exchanger, wherein the controller is configured to receive corresponding signals from each of the temperature sensors, said signals representing the temperature measured by the respective temperature sensor.
 5. The cooling system according to claim 1, furthermore comprising: a fluid line configured to branch off at least part of the first fluid flow downstream of the first heat exchanger and to supply same to the second fluid flow upstream of the second heat exchanger; and a control apparatus configured to regulate a volumetric flow of the first fluid flow branched off through the fluid line.
 6. A cooling system according to claim 1, wherein at least one of the first heat exchanger or the second heat exchanger is a matrix heat exchanger.
 7. A cooling system according to claim 1, wherein at least one of the first heat exchanger or the second heat exchanger is a skin heat exchanger.
 8. A cooling system according to claim 1, wherein at least one of the first heat exchanger or the second heat exchanger is a combination of a matrix heat exchanger and a skin heat exchanger.
 9. A vehicle with a cooling system according to claim
 1. 10. The vehicle according to claim 9, wherein a heat source cooled by the cooling system is a passenger cabin.
 11. The vehicle according to claim 9, wherein a heat source cooled by the cooling system is a cargo hold.
 12. The vehicle according to claim 9, wherein a heat source cooled by the cooling system is a cockpit.
 13. The vehicle according to claim 9, wherein a heat source cooled by the cooling system is an avionics component.
 14. The vehicle according to claim 9, wherein a heat source cooled by the cooling system is a hydraulic component.
 15. The vehicle according to claim 9, wherein a heat source cooled by the cooling system is an electronic component. 